Tubular structure



3 1967 A. v. cRossMAN TUBULAR STRUCTURE Filed Sept. '7, 1965 I INVENTOR A.VIRGINIA CROSSMAN ORNEY United States Patent 3,349,538 TUBULAR STRUCTURE A. Virginia Crossman, 201 E. Tropical Way, Plantation, Fla. 33314 Filed Sept. 7, 1965, Ser. No. 485,194 Claims. (Cl. 52-731) ABSTRACT OF THE DISCLOSURE A sectional tube, rectangular in cross-section, formed of two duplicate right angled units of only two base walls wherein are provided, inwardly of the longitudinal free edges of each unit, channels of L-shaped hook-like contour. The channels of the units are complemental and have longitudinally slidable interlocking engagement with each other to form the tube. Closure and reinforcing caps may be employed on the ends of the tubes. The tubes may be secured together at right angles to each other in knockdown condition and built up to form frames. The outer surface of each tube has longitudinally extending grooved lines blending with the sea-m line to obscure the same.

Summary This invention relates to a tubular structure, being concerned with the structure of the tube itself, and with its adaptability for use in many diverse situations. More particularly, the present tube is formed of two duplicate right angled units each adapted to interlock at their free edges slidingly with the other longitudinally thereof to provide a rectangular tubular structure. Hook-like channels extend along and are integral with each free edge of each unit. The hook-like channels of one unit are complemental to the channels of the other unit and slidably interfit therewith to form a tight joint.

The objects and advantages of the tubular structure of this invention are many. It is adaptable to volume production by an extruding process involving but one set of dies for its two duplicate units, thereby assuring uniformity and minimum cost. The seams at the juncture of the two units are all but obliterated, due both to their location on opposite sides of the completed tube adjacent diagonally opposite corners thereof, and to the application of closely spaced decorative serrations occupying much, if not all, of the area adjacent their lines of juncture, whereby to blend with and minimize the presence of the seams. The interlock provided between the duplicate angled units is strong, and the seams at the juncture lines therebetween. although of variable width, are never open except for slight surface gaps whose limits are closely fixed. Each interlock which is weather-tight serves also to prevent separation of one unit from the other except when an endwise sliding movement therebetween has proceeded to completion.

Joining of one tube to another, as in a framework, is also facilitated where the end of one tube abuts the wall of another to which it is to be secured. This may be accomplished by (1) connecting a single angled unit of a first tube to the end of a second tube whose two angled units remain completely assembled, and then (2) completing the first tube by assembling therewith a companion angled unit. There is also a closure cap applicable to either or both ends of each tube where needed for appearance and for functional purposes, this cap serving to (1) wedge the two units laterally away from each other whereby the surface gaps of the seams therebetween are widened very slightly, (2) lock the two angled units frictionally against relative endwise sliding movements, whereby to prevent separation of one from the other, and (3) provide internal reinforcement for the walls of the tube.

3,349,538 Patented Oct. 31, 1967 These and other objects and advantages presently to be noted may be realized from my invention a preferred embodiment of which is illustrated in the accompanying drawing in the manner following:

FIGURE 1 is a fragmentary view, partly in elevation and partly in section, of one tubular structure in horizontal position joined to an angled unit of a second such tubular structure, the latter being shown in cross section taken on the line 11 of FIG. 2;

FIG. 2 which is a vertical sectional view of the angled unit and a longitudinal section of a portion of the horizontal tubular structure shown in FIG. 1, both taken on line 2-2 thereof, exhibits the means by which the one is fixedly connected to the other;

FIG. 3 is a transverse sectional view, taken on line 3-3 of FIG. 2, showing two duplicate angled units interfited to produce the present tubular structure, also, in elevation, the inner face of a closure cap applied thereto;

FIG. 4 is an elevational view of the closure cap per se, looking toward its inner face;

FIG. 5 is an elevation of one open end of a somewhat similar, but different tubular structure of one-piece, showing at its opposite end the inner face of the same closure cap applied thereto;

FIG. 6 is an enlarged fragmentary end elevational view of the completed tubular structure showing portions of two of its walls and a third wall therebetween, all formed with longitudinal serrations extending continuously on opposite sides of one of the seams between its two interfitted angled units, the same as depicted on the vertical tube of FIG. 2; and

FIG. 7 is a fragmentary view similar to FIG. 6, show ing the longitudinal serrations confined to a group adjacent a seam of the tube, the same as depicted on the horizontal tube of FIG. 2.

A framework wherein the present tubular structure (herein frequently called a tube) may be advantageously used is commonly found in furniture pieces such as stands, tables, beds, cabinets, chairs, etc. (for dolls, children and adults). The tubes of this invention are also suitable for suspending draperies, for partitions and room dividers, and outdoors they may be used for screen frames and doors and for screened enclosures; they may also be used as conduits for electrical wiring both indoors and out. These are just a few of its many applications. The size, shape, color, finish and ornamentation of the tubular structures may be varied according to the requirements of their intended use and to the tastes of those using them. Production of the tubular structures may be achieved advantageously and economically from suitable materials which are formable under conditions of heat and pressure when extruded through dies appropriate for the purpose. Aluminum alloys and certain plastic compositions are examples. All such completed products are substantially inflexible.

The incomplete framework illustrated in FIG. 2 utilizes two tubular structures V and H joined together, the former extending vertically to provide support for the latter (H) which is disposed horizontally with its opposite ends abutting sides of the vertical tubes to which it is fixedly connected. As best shown in FIGS. 1 and 3, each tube consists of two elongated duplicate angled units a and b, each having base walls x and integrally joined together longitudinally in right angled relation. The thickness of these walls, say .050", is desirably uniform at every point. The longitudinal free edge portion of the base wall x is inturned by right angle bends through degrees to provide a first hook-like channel facing toward the other Adjacent the longitudinal free edge of the other base wall y, but spaced slightly therefrom, is a second hooklike channel which faces laterally away from the base wall x. This latter channel of L-form is provided by a U-wall having a leg 15 fixedly disposed normally of the base wall y at a point well inwardly of its longitudinal free edge. This U-wall includes also a relatively short lip 17 inset from the longitudinal free edge of the base wall y by a distance which is substantially equal to the thickness thereof. This lip which is parallel with the lip 10 of the first channel is also spaced from the leg 15 by a distance very slightly greater than its own thickness.

' The lip 16 terminates short of the base wall y by a distance slightly greater than the thickness of the wall to form therewith and with the leg 15, the second channel which has a lateral opening thereinto facing away from the leg 15. The two angled units thus formed are both duplicates and complementary to each other in that the lip of the first channel is adapted, when advanced endwise toward the second channel and in alignment therewith, to fit slidingly therein while the lip 16 of the latter channel is similarly received into the first channel (FIG. 3). The two angled units, when so assembled, are closely interfitted with but slight clearance therebetweenjust enough, and no more, to approach closely a minimum of frictional resistance when slid one upon the other. In the tubular structure thus produced the exterior face of each of its walls is uniplanar with two exposed seams s disposed adjacent diagonally opposite corners of the tube, the presence of these seams being obscured by means later to be described.

Also provided on the inner face at each base wall at a mid point transversely thereof is an incomplete circular tube extending through approximately 270 degrees to form an outwardly bowed channel 25. As shown best in FIG. 3, the gaps in these channels on adjacent base walls x and y are faced angularly toward each other to facilitate their production with the aid of extrusion dies. These channels extend for the full length of each angled unit to terminate coplanarly therewith. The size and shape of each bowed channel is such as to receive into either end portion thereof a self-tapping screw S which, when rotatively advanced thereinto, forms cooperating threads therein. When so advanced into one of the bowed channels, the screw becomes firmly anchored therein whereby to fixedly connect thereto any part traversed by the screw shank to provide support therefor.

In FIG. 2 the horizontal tube H is shown as having one of its ends abutting the base wall y of the angled unit a, also its opposite end abutting the base wall y of the vertical supporting tube V, with screw connections therebetween. In the operation of assembling these tubes into a framework, the angled unit b (or a) of each vertical tube is shifted endwise of the other unit a (or b), or removed therefrom, so as to expose one or more holes [1 formed through the latters base wall y (or x) which abuts the open end of the horizontal tube. These holes, when located in the angled unit at a mid point transversely of its base wall x or y, as the case may be, will then lie opposite two of the bowed channels 25 in the base walls of the tubular structure H to register axially therewith. A screw S may then be advanced through each hole I: and on into the registering bowed channel 25 to form therein screw threads with which it remains engaged, the screw head finally engaging the angled unit a (or b) to fixedly connect it to the tube H. FIG. 1 illustrates two such screws to fixedly secure one end of the horizontal tube H to the angled unit a preliminary to its assembly into a vertical tube, the head of one of these screws engaging one of the bowed channels 25 in the angled unit a which is disposed oppositely of one of the like channels 25 in the tube H. A second screw S is also shown disposed laterally of the bowed channel in the angled unit a at a point which coincides with one of the bowed channels in the tube H. As suggested in FIG. 2, a third screw S may also be employed in this connection by locating it directly below the first mentioned screw to traverse the same bowed channel in the angled unit a. In the operation of rotatively advancing each screw to locking position within one of the bowed channels 25 in the horizontal tube, it will be noted the screw head is at all times fully exposed so as to be accessible for engagement by a driving tool or the like; subsequently, however, the angled unit 12 (or a) previously removed or shifted from its companion unit a (or b) is slidingly restored to its properly assembled position therewith, opposite ends of the two units being then coplanarly disposed whereby to complete the vertical tube and bar all further access to the screw or screws S whose presence is thereupon concealed for all time.

With the two angled units assembled in interlocking relation, two seams s are formed along their lines of juncture to be visible exteriorly of the tube. The seam lines thus formed which are relatively narrow extend longitudinally upon two opposite sides of the tube adjacent diagonally opposite corners thereof and removed therefrom by a slight distance corresponding to its wall thickness in each case. The presence of these seams is further minimized by exterior ornamentation applied to the tube, extending for its full length in the form of a plurality of grooved lines 1 each having, by preference, a serrated profile. The groove-forming operation may be performed as part of the extruding process. These serrations are too small to be exhibited satisfactorily in FIGS. 1 and 3, but are depicted with fair clarity in the enlarged views. FIGS. 6 and 7. According to FIG. 6, each seam lies between one of the grooved lines I on the same wall of the tube and an exposed edge e of one of the angled units (FIG. 3), the sharp corners of the tube being broken by curvatures of very small radius. The edges e of the base walls x and y which are exposed at diagonally opposite corners of the tube are also rounded so as to reduce the width of their flat areas very slightly (FIG. 6). The radius of curvature at the tube corners should desirably be short, possibly less than half the thickness of the tube walls. This feature of rounded corner-edges is one factor in deemphasizing the appearance of the adjacent seams s whose presence is thereby blended with the surrounding areas.

It is desirable that a group of grooved lines I in an adequate number be located adjacent each seam line to achieve the obliterating effect just noted. These grooves should be contiguous, or be spaced closely apart, both with respect to each other and to the adjacent seam lines, and their widths should preferably approximate that of the seams, when expanded. Beyond these simple requirements it is possible to vary the disposition and character of the grooved lines over the tube exterior to produce different ornamental effects. Certain examples of this are suggested in the drawing. Since there is no seam present in the wall of the tube H as shown in FIG. 1, there is no need for having any grooved lines thereon, and none is shown. It is optional whether to decorate such a wall surface with a few or many grooved lines, or none at all. By contrast, the horizontal tube H if FIG. 2 shows a wall having a seam line s together with a small number of grooved lines I in the wall surface adjacent thereto so as to blend therewith. The grooved lines I in this group are spaced apart from each other and from the seam line 5 by a distance approximating the width of the exposed wall edge e and, as shown in FIGS. 2 and 7, they are confined to an area proximate to the seam to obliterate its presence as a distinct entity. And in the vertical tube V of FIG. 2, the grooved lines I cover the entire surface of the seam-wall there shown, including the exposed wall edge e, these grooves being contiguous both to each other and to the seam itself. Each of these illustrated examples has in common the feature of a plurality of grooved lines I spaced closely apart from each other and from the seam line s whose separate presence is thereupon erased for all practical purposes.In this connection, I would have it understood that by the term spaced closely apart I include any spacing between contiguity and separation by a distance approximating the width of each exposed wall edge e.

I have also illustrated in FIGS. 1, 2 and 6 a grooved line c located at a mid point centrally of one side of the tube, to be duplicated on each of its walls, if desired. This center line is slightly heavier than the remaining grooved lines I, if there be any such lines proximate thereto as shown in FIG. 6. Its purpose is not to be conspicuous, but just to be discernible to a workman when looking for it. For example, if the grooved lines I be .008" deep, the depth of the center lines a need not be more than .012". These center lines do not aifect or impair the decorative value of the grooved serrations, but they do serve the functional purpose of facilitating location of a screw hole or holes h to be formed at a mid point through a wall of a vertical or horizontal tube. When completed, each hole will then receive a fastening screw S at a point which is directly opposite one of the bowed channels 25 in a horizontal tube, for example, which is to be fixedly secured to a vertical tube in the manner already described. In the tubes thus joined, the outer or front faces, as well as those upon the rear, will be assured of coplanar dispositions. The entire system of grooved lines I, if extended continuously around all four sides of the tube, or grouped esthetically on just its seamwalls, will produce a decorative background in which both the seam lines s (and possibly also the center lines o) are engulfed andsubstantially lost to view-a highly desirable feature in a tubular structure of the general kind herein discussed. In many cases, the vertical tube will serve as a post or leg to which will be affixed two right .angularly diverging horizontal tubes disposed at a common level; the operation of installing fastening means will then proceed as already described, the holes h being then formed through both base walls x and y of the same vertical angled unit, instead of but one of them.

One remaining feature of this invention remains to be considered, viz.', the closure cap C for each open end of the tubular structure. Such a cap is shown per se in FIG. 4, and in applied position in FIGS. 2 and 3. This cap has the special functional purpose in connection with the present two-unit tubular structure of wedgingly exerting outwardly thrust forces transversely of the tube, tending to crowd one angled unit away from the other and, in so doing, to do three things, viz.: 1) enhance their frictional resistance to sliding movements whereby to prevent a too-ready separation of one from the other, (2) shift one unit laterally away from the other to a limit which is fixed by the very slight clearance between their interfitting hook-like channels, and (3) provide internal reinforcement for the walls of the tube. And as a further objective, the special means for this purpose also adapts the cap for successful application to the modified one-piece tubular construction of FIG. 5.

The cap, as shown, is essentially a disk 30 of substantially the same dimensions and cross sectional shape as the tube for which it is designed, perhaps even slightly larger for appearance sake, thereby adapting it to fit upon and over either open end of the tubular structure already described. Desirably the cap is formed from some such material as a synthetic plastic composition with four L-walls t, u, v and w depending from the under or inner face of the disk. As shown best in FIG. 4, these walls are much alike in contour with all Ls substantially the same in length, each being located in a corner portion of the disk where they are arranged with their Ls parallel with two of the disk edges, but the disposition of two of these Ls-walls is opposite that of the other two. The L-walls t and v occupy diagonally opposite corner positions of the disk with their angles located a maximum distance from its corners, the remaining corner portions being occupied by the L-walls u and w with their angles 6 relatively close to the disk corners. The spacing between these L-walls is such that when the cap C is properly fitted over the end of the tubular structure, its L-walls will be advanced into the interior thereof (FIG. 2).

The cap, when applied to the tube, will occupy either of two rotative positions degrees apart in which each of the L-walls t and v (with angles remote from the disk corners) laps past 1) one of the channel U-walls to engage the two base walls x and y, also (2) the proximate faces of the twogbowed channels carried thereby at points relatively close ,to two diagonally opposite corners of the tube (see FIG. 3). When so disposed, the other L- walls I: and w (with angles close to the disk corners) lie wedgingly against the base walls x and y at points close to the two remaining diagonally opposite corners of the tube, being also engaged with faces of the two bowed channels proximate thereto. The fit of the L-walls against the tube walls so engaged may be varied, as desired, and by tapering the angled walls appropriately for the purpose the cap, when applied to the tube, may be secured thereto with a drive fit so as to remain frictionally assembled therewith. The thrust forces created by advance of the cap L-walls into the interior of the tube tend to wedge the two angled units away from each other through the limited distance permitted by the very slight gap existing in the interlock between their interfitting channels. The cap herein illustrated may also serve usefully as a foot for a vertical tubular structure, when applied to its lower end, or be equipped with an ornamental head piece when the place of its use so justifies.

As hereinbefore noted, there is a very slight clearance between the two hook-like channels when they are interfitted to interlock the two angled units a and b. This clearance is necessary both to facilitate correct positioning of the ends of the two units when inter-fitting assembly thereof is initiated, and to materially reduce friction therebetween when one is to be slid longitudinally of the other. Desirably the extent of this clearance should be as small as practicable so as to hold lost motion therebetween to a minimum. In commercial production of the angled units forming the present tubular structure, it is feasible to hold the clearance between its two angled units to .005" or thereaboutsa clearance too small to be undistortably illustrated herein, yet wide enough, when present in a gap in each of the seams s, to be noted upon close observation. To minimize the appearance of such a gap, the width of each grooved line I in the group adjacent a seam s approximates that of the seam itself when fully expanded. To assure such expansion, the closure caps C are provided with L-walls extending inwardly of opposite ends of the tubular structure to wedgingly engage with inner faces of its walls and exert thereon lateral pressures tending to shift the two angled units 01 and b laterally away from each other. These opposing pressures in substantially equal degree may be directed against all four walls of the tube or against only one pair thereof, depending largely upon the spaced-apart positions of the opposite L-Walls. Such opposing pressures are also exerted independently by each of the L-wa1ls. In any event, it is contemplated that opposite pressures shall be applied laterally to the base Walls y of the two angled units a and b in directions parallel to the lips 10 and 16 whereby to produce a lateral shifting of one unit away from the other as far as permitted by the clearances between their interfitting hook-like channels. By this means and in this manner, I provide for each seam s a fixed limit to the variable width of its surface gap, corresponding generally to the widths of the adjacent grooved lines 1, thereby assuring an effective blending of one with the other. 1

The one-piece rectangular tube T of FIG. 5 is shown as provided with four bowed channels 35, one on the inner face of each of its four sides at a mid point transversely thereof. When produced in the same dimensions as the two-part tubular structure of FIGS. 1-3, the cap C may be fitted thereto to position its L-walls in engagement with the interior faces of the tube, including opposite sides of each of its bowed channels, in exactly the same way as already described. With the cap so applied to one end of the tube, the L-walls provide thereat internal reinforcement for the tube walls to resist any inward deflection thereof in response to pressure or impact from a blow exteriorly thereof. By providing for a tight or snug fit between the engaging faces of the cap and tube, retention in place of the cap, through friction alone, may be assured for an indefinite period.

I claim:

1. A tubular structure comprising two substantially inflexible, duplicate right angled units of equal length each consisting of only two elongated base walls of uniform thickness joined together longitudinally in right angled relation, a flange inturned along the free longitudinal edge of the first base wall and double bent to provide a lip spaced therefrom and defining therewith a first channel, the channel being faced toward the second base wall, and a U-wall having a leg disposed normally of the second base wall and fixedly secured thereto at a point remote from its free longitudinal edge, said U-wall including a relatively short lip inset from the free longitudinal edge of the second base wall by a distance substantially equal to the thickness 'thereof, the lip being spaced from the leg and terminating short of the second base wall by a distance substantially equal to the thickness thereof to form therewith and with the leg a second channel having a lateral opening thereinto adjacent the second base wall and facing away from the first base wall, the two angled units and the two channels thus formed being complementary to permit the lip of the first channel to fit slidingly within the second channel, and vice versa, whereby the two angled units are interlocked together to form a rectangular tubular structure having four uniplanar sides with two exposed seams adjacent diagonally opposite corners thereof.

2. A tubular structure according to claim 1 wherein a plurality of grooves are formed longitudinally of the outer faces of the two angled units whereon the seams appear, the grooves being closely spaced apart from each other and from the seams to blend therewith and minimize the presence thereof.

3. A tubular structure according to claim 1 wherein means is provided for preventing relative longitudinal movements between the two angled units when their ends are coplanarly disposed, comprising a cap fitted over an open end of the tubular structure and provided with walls extended normally from its inner face for engagement with interior faces of both angled units, adapted to exert opposing thrust forces thereagainst to provide internal reinforcement therefor and enhance frictional pressure between the angled units when the cap is advanced into engaging position relative thereto.

4. The structure called for in claim 1, wherein a plurality of said tubular structures are joined together with the end of one abutting the side of another to form a framework; each angled unit thereof being also provided on its inner face at a mid point transversely thereof with a bowed channel extending for the length thereof, the two angled units of each tubular structure being free for relative sliding movements to expose their inner faces for varying distances whereby to permit facile application of screw fastening means through a base wall hole in one angled unit at a mid point transversely thereof for entry into the open end of an abutting tubular structure to engage the proximate longitudinally bowed channel thereof for securing one angled unit to the other and, when the two angled units are repositioned longitudinally with their ends in coplanar relation, to cover the screw fastening means so disposed interiorly of the tubular structure.

5. A framework according to claim 4 in which exposed open ends of the tubular structure are closed by application thereto of caps adapted to rest against the end of the angled units, each cap being provided with walls extended normally from its inner face for frictional engagement with opposite interior faces of both angular units, adapted to exert thereagainst opposing thrust forces whereby to provide internal reinforcement therefor and enhance frictional pressure between the angled units when the cap is advanced into engaging position relative thereto.

References Cited UNITED STATES PATENTS 950,806 3/1910 Richardson 52301 3,143,165 8/1964 Lewis et a1. 52-731 3,170,201 2/1965 Nofziger 52--731 3,216,170 11/1965 Deadrick 52-731 3,222,841 12/1965 Lipof 52731 3,256,659 6/1966 Dudoff 52301 3,305,221 2/1967 Kling 25624 X BOBBY R. GAY, Primary Examiner.

A. CALVERT, Assistant Examiner. 

1. A TUBULAR STRUCTURE COMPRISING TWO SUBSTANTIALLY INFLEXIBLE, DUPLICATE RIGHT ANGLED UNITS OF EQUAL LENGTH EACH CONSISTING OF ONLY TWO ELONGATED BASE WALLS OF UNIFORM THICKNESS JOINED TOGETHER LONGITUDINALLY IN RIGHT ANGLED RELATION, A FLANGE INTURNED ALONG THE FREE LONGITUDINAL EDGE OF THE FIRST BASE WALL AND DOUBLE BENT TO PROVIDE A LIP SPACED THEREFROM AND DEFINING THEREWITH A FIRST CHANNEL, THE CHANNEL BEING FACED TOWARD THE SECOND BASE WALL, AND A U-WALL HAVING A LEG DISPOSED NORMALLY OF THE SECOND BASE WALL AND FIXEDLY SECURED THERETO AT A POINT REMOTE FROM ITS FREE LONGITUDINAL EDGE, SAID U-WALL INCLUDING A RELATIVELY SHORT LIP INSET FROM THE FREE LONGITUDINAL EDGE OF THE SECOND BASE WALL BY A DISTANCE SUBSTANTIALLY EQUAL TO THE THICKNESS THEREOF, THE LIP BEING SPACED FROM THE LEG AND TERMINATING SHORT OF THE SECOND BASE WALL BY A DISTANCE SUBSTANTIALLY EQUAL TO THE THICKNESS THEREOF TO FORM THEREWITH AND WITH THE LEG A SECOND CHANNEL HAVING A LATERAL OPENING THEREINTO ADJACENT THE SECOND BASE WALL AND FACING AWAY FROM THE FIRST BASE WALL, THE TWO ANGLED UNITS AND THE TWO CHANNELS THUS FORMED BEING COMPLEMENTARY TO PERMIT THE LIP OF THE FIRST CHANNEL TO FIT SLIDINGLY WITHIN THE SECOND CHANNEL, AND VICE VERSA, WHEREBY THE TWO ANGLED UNITS ARE INTERLOCKED TOGETHER TO FORM A RECTANGULAR TAUBULAR STRUCTURE HAVING FOUR UNIPLANAR SIDES WITH TWO EXPOSED SEAMS ADJACENT DIAGONALLY OPPOSITE CORNERS THEREOF. 